# 8.9 Investigation and Experimentation

Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other three strands, students should develop their own questions and perform investigations. Students will:
1. Plan and conduct a scientific investigation to test a hypothesis.
2. Evaluate the accuracy and reproducibility of data.
3. Distinguish between variable and controlled parameters in a test.
4. Recognize the slope of the linear graph as the constant in the relationship y=kx and apply this principle in interpreting graphs constructed from data.
5. Construct appropriate graphs from data and develop quantitative statements about the relationships between variables.
6. Apply simple mathematic relationships to determine a missing quantity in a mathematic expression, given the two remaining terms (including speed, density, pressure, and volume).
7. Distinguish between linear and nonlinear relationships on a graph of data.

## What the Standard Means - Student Speak

For standard 8.9 students need to be able to design and conduct their own experiment.........
8.9a- to make a scientific investigation to test a hypothesis
8.9b- to calculate the data accuracy and reproducibility
8.9c- to find the difference between variable and controlled parameters in a test
8.9d- understanding a linear graph (y=kx) linear and nonlinear relationships on a graph
8.9e- to build a correct graph from data and make quantitative statements about relationships in variables
8.9f- to use math skill to determine a missing quantity in a mathematic expression
8.9g- to know the difference between linear and nonlinear relationships

The Scientific Method
The Scientific Method is a way scientists answer questions and solve problems. When scientists look for answers, they mostly use the same steps. But there is more than one way to use each step. Scientists use either all of the steps or just a few during an investigation. Some may even repeat some steps or do them in a different order. Choosing a way to use the steps is based on what works best to accurately answer the question. Scientific methods provide a framework for conducting careful investigations and understanding the natural world.

 Steps of the Scientific Method

Accuracy and Reproducibility of Data
When a scientist conduct an experiments, they want to collect correct data. They want the answer to be correct. If you place 701 g on a balance and get a mass reading of 152 g, your reading is not correct. Maybe you’re using broken equipment, using the wrong tool, or using a tool incorrectly.
Using a graduated cylinder to measure volume can give a more accurate measurement than using a measuring cup found in the kitchen. Your data will still be wrong if you do not read the volume at the bottom of the meniscus at eye level. To get a correct reading using a ruler, you should look straight down on the end of the object you are measuring. If you move your head to either side, you will get a somewhat different measurement.
When a scientist conducts an investigation, they want their results to be able to be frequent, or reproduced, by other scientists. If the data are not reproducible, then there is no way for the results of the experiment to be supported and acknowledged by other scientists. Data must be reproducible in order for other people to be in agreement with your conclusions.
When scientists analyze data, they often find it helpful to use a single number to describe the entire set of data. Three terms that are used for this purpose are mean, median, and mode. The mean is found by adding all the data points together, then dividing the sum by the total number of data points. Mode is the number that appears most often in a data set. And median is the value of the data point in the middle when the data are placed in order from smallest to largest. The median is especially helpful when one data point is much smaller or larger than the rest of the data points.
To find the slope of a line, it is helpful to use rise over run. Rise represents a vertical (up and down) change. Run represents a horizontal (side to side) change. For a line on the coordinate plane, the change in y, or the rise, indicates the number of units moved up or down. The change in x, or the run, is the number of units moved to the right or left. Slope is found by dividing the vertical change (the change in y) by the horizontal change (the change in x). In other words, the slope of a straight line is found by dividing the rise by the run, often described as rise over run.

Linear and Nonlinear Graphs
 Linear Graph
aight line shows how much one factor (y) changes in relation to another factor (x). A straight line shows that a regular linear relationship exists between the factors you are studying. Y always changes the same amount in relation to x. Many relationships that scientists study are not linear. In a nonlinear graph, each unit changes in one factor (y) do not always bring the same change in another factor (x). The graph of this relationship will be a curve instead of a straight line. There is a nonlinear relationship between the factors being studied.
 Nonlinear Graph

Making a Graph
Data tables help you arrange data. Graphs help you understand and use that data. Graphs make it easy to recognize trends and make predictions. A graph has a horizontal (side to side) x-axis and a vertical (up and down) y-axis. The x-axis more often than not represents the independent variable in the data table. The y-axis more often than not represents the dependent variable. Each axis is labeled with the name of the variable that is represented.
Each axis has its own range. To find the range, subtract the smallest value of a single variable from the largest value of the same variable.
The next step is to decide the scale of the graph. Each axis has its own scale. The scale is the size that is used for each box or grid mark on the graph.
The data points need to be plotted now. We plot the data points by putting a dot on the graph for each pair of data in the data table. Every so often, a “line of best fit” is needed. A line of best fit is a smooth line that is drawn to “fit,” or to include, some but not all of the data points. The smooth line without sharp turns or sudden bends shows the pattern described by the data. The line of best fit in addition shows how the data varies from the pattern.
The very last step is to give the graph a name. The name helps people recognize what the graph describes. Scientists often include the independent and dependent variables in the name.

Finding a Missing Quanity

Speed=Distance/Time

Density=Mass/Volume

Force=Pressure x Area

Volume=Area x HeightReview Questions
-The is the factor that the experimenter changes. Dependant Variable
-In an experiment, the mass of each 5 apples is measured. The results are 95 grams, 85 grams, 90 grams, 85 grams, and 100grams. Identify the mode.85 grams
-What is the value of the data point in the middle of a set of data when the data are arranged in order from smallest to largest? Median
-In a scientific investigation, the purpose of an experiment is to ?Test a hypothesis
-A hypothesis is ___. A possible answer to a question